Connector for multiconductor pacing leads

ABSTRACT

A cardiac pacing lead having a plurality of individually insulated conductors arranged as a multifilar coil. The lead includes a connector assembly and a ring electrode assembly, each of which are optimized for use in conjunction with conductors arranged in the form of a multifilar coil. The connector assembly takes the form of an in-line connector having a plurality of linearly arranged connecting surfaces, each coupled to one of the conductors in the multifilar coil. The ring electrode assembly is constructed such that it displays the same outer diameter as the pacing lead. In both assemblies, conductors are coupled by means of welds, rather than by crimping or swaging.

This is a divisional of application Ser. No. 198,540, filed on May 25,1988, now U.S. Pat. No. 4,922,607.

BACKGROUND OF INVENTION

The present invention relates to medical electrical leads generally, andmore particularly to cardiac pacing leads.

Early pacing leads, such as those disclosed in U.S. Pat. No. 3,348,548and U.S. Pat. No. 3,788,329 employed separate conductor coils in aside-by-side or coaxial configuration, insulated from one another byplastic sheaths which covered the coils. More recently, multifilarcoiled conductors having individually insulated coil wires have beenpursued, as disclosed in Canadian Patent No. 1,146,228 for a MULTIPOLARPACING CONDUCTOR, issued May 10, 1983 to Upton. This patent discloses asingle, multiconductor DBS coil having individually insulated wires, andis incorporated herein by reference in its entirety.

SUMMARY OF THE INVENTION

The present invention is directed toward optimizing the construction ofa pacing lead or other medical electrical lead of the type employingmultiple, mutually insulated conductors, arranged in the form of amultipolar coil. In particular, the invention is directed towardimproved connector assemblies and ring electrode assemblies for suchleads.

Typically, in pacing leads employing a plurality of conductors, each ofwhich are formed as a separate coil, connection of the coil to anelectrode or a connector pin has been accomplished by means of crimpingor swaging these components to one another, as disclosed in U.S. Pat.No. 4,258,725, issued to O'Neill and U.S. Pat. No. 4,328,812, issued toUfford et al. However, where the conductors take the form of amultifilar coil, additional problems are presented. The conductors mustbe split off from the coil individually, and routed to the desiredconnector surface or electrode surface, without comprising themechanical integrity of the lead at that point. Because one of theadvantages of a multiconductor coil is that it allows fabrication of asmaller diameter lead, it is especially desirable to avoid unnecessarybulk in the vicinity of these assemblies.

The present invention addresses these problems by providing connectorand electrode assemblies which are constructed to allow all electricalconnections to the conductors to be made by welding. This allows for theelimination of crimping or swaging cores commonly used in prior artleads. In addition, the connector and ring electrode assemblies aredesigned to provide increased structural integrity and improved sealingdue to the use of hot-melt and adhesive backfill procedures duringmanufacture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a bipolar cardiac pacing lead according tothe present invention.

FIG. 2 shows a sectional view of the lead of FIG. 1 in the vicinity ofthe connector assembly.

FIG. 3 shows an alternative connector assembly for use with a tripolarlead.

FIG. 4 shows a sectional view of the lead of FIG. 1 in the vicinity ofthe ring electrode.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a pacing lead employing improvements accordingto the present invention. At the distal end of the lead is located apacing electrode 10, which may be fabricated according to any of avariety of well known electrode types. Preferably, the electrode isfabricated according to the disclosure in U.S. Pat. No. 4,506,680,issued to Stokes, and incorporated herein by reference in its entirety.Electrode 10 is held in place within the heart by means of pliant tines12, which are more fully described in U.S. Pat. No. 3,902,501, issued toCitron et al, also incorporated herein by reference in its entirety.

The lead includes an elongated insulative sheath 14, which extends fromthe connector assembly 16 to the ring electrode 18. The lead alsoincludes a second insulative sheath 20, extending from ring electrode 18to electrode 10. Mounted around insulative sheath 14 is a suture sleeve17, which is used to anchor the lead at the point of venous insertion.Connector assembly 16 includes a connector pin 24 and a connector ringassembly comprising an exposed ring shaped member 22. Insulative sleeve26 separates pin 24 from ring member 22. Insulative sleeve 28 extendsdistal to ring member 22. The connector assembly is provided withresilient sealing rings 30 and 32, which seal the connector assemblywithin a corresponding receptacle mounted to a cardiac pacemaker. Thearea of the lead enclosed by dashed line 34 is illustrated in moredetail in FIG. 2. The area of the lead enclosed by dashed line 36 isillustrated in more detail in FIG. 4.

Insulative sleeves 26 and 28 are preferably fabricated of siliconerubber. Insulative sheaths 14 and 20, are preferably fabricated ofpolyurethane or silicone rubber. Connector pin 24, ring member 22, ringelectrode 18 and tip electrode 10 are preferably fabricated of inertconductive metals such as platinum, Elgiloy® alloy, MP35N or stainlesssteel.

FIG. 2 shows a sectional view of the proximal portion of connectorassembly 16, illustrated in FIG. 1. This view shows the interconnectionof the multiconductor coil 34 with the other components of connectorassembly 16, illustrated in FIG. 1. Components visible in FIG. 1 arelabeled similarly in FIG. 2. Multiconductor coil 34 includes a firstcoiled conductor coupled to connector pin 24 and a second coiledconductor electrically coupled to ring member 22.

The connector assembly is fabricated by first laser welding ring member22 to cylindrical member 36 by means of a circumferential laser weld at38 to form a connector ring assembly. Assembled ring member 22 andcylindrical member 36 are assembled over connector pin 24, placed into amold, and insulative sleeve 26 is then injection molded between them.This process is disclosed in more detail in U.S. Pat. No. 4,572,605,issued to Hess and incorporated herein by reference in its entirety.

The completed assembly of connector pin 24, insulative sleeve 26, ringmember 22 and tubular member 36 is then coupled to one conductor 40 ofmulticonductor coil 34. Conductor 40 is screwed onto the distal end ofconnector pin 24, with protrusion 42 acting as a screw thread. Conductor40 is screwed onto connector pin 24 until its proximal end butts upagainst circular flange 44. Conductor 40 is then coupled to circularflange 44 at 46 by means of a spot laser weld. The spacing intermediatecircular flange 44 and protrusion 42 allows for a limited amount ofstrain relief immediately distal to the spot laser weld at 46.

Tubular extension 48, which takes the form of a cylinder having anextended longitudinal slot 50 is then slid over the distal end ofcylindrical member 36 and coupled to it by means of a circumferentiallaser weld at 52. A shallow grooved section 52, having a groove thatcorresponds generally to the size of conductor 54, is located at theproximal end of slot 50 in tubular extension 48. Conductor 54 isstripped of insulation and laid lengthwise in the grooved area 52, andlaser welded to extension 48. Following this step, insulative sleeve 28is slid over extension 48 and over cylindrical member 36. Member 36 isprovided with a cross bore 56, which may be filled with medicaladhesive, thereby bonding insulative sleeve 28 to insulative sleeve 26.

Finally, the entire assembly is backfilled with adhesive injectedbetween insulative sheath 14 and insulative sleeve 28, filling the areabetween insulative sleeve 28 and sheath 14, as well as the lumen 58 ofsleeve 28 and the lumen 60 of tubular extension 48. This serves to bondthe components of the connector assembly to one another and toinsulative sleeve 28 and to electrically insulate the conductor 40 andconnector pin 24 from the conductor 54. For the sake of clarity, thebackfilled adhesive is not shown in this illustration. Mounted withinmulticonductor coil 34 is a Teflon® plastic liner 62, which serves as apassageway for a stylet. The internal lumen of liner 62 is aligned withthe internal bore 64 of connector pin 24.

FIG. 3 shows an alternative connector assembly adapted for use with atripolar, coaxial lead. This figure illustrates how sequentialapplication of the basic techniques disclosed in conjunction with thebipolar lead can be used to produce a tripolar or multipolar connectorhaving sequential, ring shaped connector surfaces.

The connector assembly of FIG. 3 is fabricated by first assemblingconnector ring 122 over connector pin 124, placing them in a mold andsubsequently injection molding insulative sleeve 126 between them. Thisprocess is disclosed in the above cited Hess patent. Connector pin 124is provided with a lumen 120 through which a stylet may be inserted.Connector ring 122 is provided with two perpendicular bores 123 whichare filled by sleeve 126 during the molding procedure. The assembly ofconnector pin 124, sleeve 126 and connector ring 122 is then coupled tothe inner conductor coil 140. Conductor coil 140 is slipped over thedistal end of connector pin 124, and held in place by means of crimpingsleeve 142. Insulative sleeve 141 is then slid over inner conductor 140.

After attachment of inner conductor 140 to the distal end of connectorpin 124, tubular extension 148, which takes the form of a cylinderhaving a longitudinal slot 150 at its distal end and second connectorring 200 are assembled in their respective positions in an injectionmold, and insulative sleeve 202 is injection molded between them.Connector ring 200 is provided with two perpendicular bores 201 whichare filled by sleeve 202 during the molding process. This assembly isthen slid over the distal end of connector ring 122 and coupled to it bymeans of a circumferential laser weld at 152. After this step, theproximal ends of two of the individual conductor wires 135 of multifilarcoil 134 are stripped of insulation and laser welded to tubularextension 148 in slot 150. Following this step, a second tubularextension 204 is slid over tubular extension 148. Second tubularextension 204 is welded to second connector ring 200 by means of acircumferential laser weld at 203. Tubular extension 204 includes anelongated slot 208 and a shallow grooved section 210 at its distal end.The proximal ends of the two other conductors 137 from multipolar coil134 are stripped, laid in shallow groove 210 and laser welded withingroove 210. Outer insulative sheath 220 is then slid over multipolarcoil 134.

After these steps have been completed, a sealing ring/strain reliefmember 212 is applied around the second connector ring 200. Because ofthe penetration of the material of sleeve 202 through bores 201, member212 can be bonded directly to insulating sleeve 202 using a suitableadhesive. This provides a better bond than would be available if member212 were bonded directly to connector ring 200. If sleeve 202 andsealing ring member 212 are both fabricated of silicone rubber, asilicone medical adhesive would be appropriate.

The interior of the assembly is backfilled with silicone adhesive 222through bore 224, which extends through second connector ring 200,sleeve 202 and tubular extension 148. Backfilling continues until theadhesive is visible within the lumen of sealing ring/strain reliefmember 212, distal to tubular extension 204. This seals the lead,provides additional electrical insulation, and internally bonds thecomponents together for added mechanical strength.

A second sealing ring member 214 is applied exterior to first connectorring 122. Because sleeve 126 extends through bores 123, sealing ringmember 214 may be bonded directly to sleeve 126, using a suitableadhesive.

Surrounding sealing ring strain relief member 214 is a locking sleeve218, which is intended to be used in conjunction with a deflectable beamlocking member on the connector housing into which the lead is inserted.This connector system is disclosed in more detail in copending, commonlyassigned U.S. patent application Ser. No. 184,903, for IN-LINE PACEMAKERCONNECTOR SYSTEM, filed Apr. 22, 1988, by Terry Daglow and RichardSandstrom, and incorporated herein by reference in its entirety.

Connector rings 122 and 200, connector pin 124, tubular extensions 148and 204 and crimp sleeve 142 may all be fabricated of an inert,biocompatible metal such as stainless steel. Sleeves 126 and 202 andsealing ring members 212 and 214 are preferably fabricated of siliconerubber. Sheaths 141 and 220 and locking sleeve 218 are preferablyfabricated of polyether urethane.

By repeated duplications of the connector rings, insulating sleeves andtubular extensions, a connector assembly having any number of linearilyarranged connector rings may be produced. The particular configurationof the components allows for the use of laser or resistance welding toaccomplish all metal to metal connections, leading to increasedreliability and improved reproducibility during production. Therefore,both the method of fabrication of this connector assembly and theresultant product are believed to be a substantial improvement overprevious in-line connector designs.

FIG. 4 shows a sectional view of the area adjacent the ring electrode18, illustrated in FIG. 1. In this view, the interconnection of theconductor 54 and ring electrode 18 is illustrated. Ring electrode 18takes the form of a metal cylindrical tube, having a slot 64 adjacentits distal end. The stripped end of conductor 54 is laser welded to theend of slot 64 in electrode 18 at 66. This provides the electricalconnection between the conductor and the ring electrode. The mechanicalconnection between the various parts of the electrode is provided bymeans of a plastic sleeve 66, which is preferably fabricated ofPellethane® 2363-80A polyether urethane. Pellethane® 2363-55D polyetherurethane may also be used.

The ring electrode 18 is accomplished by first sliding sleeve 66 overthe multifilar coil 34. Conductor 54 is brought out through a hole insleeve 66. Then the assembly of coil 34 and sleeve 66 is inserted into acylindrical mold having a diameter slightly less than the inner diameterof the ring electrode 18. Heat is applied, causing the insulative sleeveto heat bond to multifilar coil 34. This also causes sleeve 66 to flowbetween the conductors of multifilar coil 34, stabilizing it in the areaof the electrode. Ring electrode 18 is slid over sleeve 66, and thestripped end of conductor 54 is laser welded to ring electrode 18 at 69.At the ends of sleeve 66, medical adhesive 68 and 70 is provided,bonding the insulative sleeve 66 to the multifilar coil 34 and to theliner 62. This structure provides mechanical integrity to the assemblyand acts as a strain relief. Insulative sheaths 14 and 20 are then slidover the ends of insulating sleeve 66, and the assembly is inserted intoa cylindrical mold having a diameter corresponding to the outer diameterof ring electrode 18. Heat is applied, causing insulative sleeve 66 toheat bond to ring electrode 18 and to insulative sleeves 14 and 20. Theresultant structure provides a lead having a uniform outer diameter inthe vicinity of the ring electrode. The bonding of sleeve 66 to sheaths14 and 20 provides a continuous electrically insulative and fluid tighttube which extends the length of the lead. During heating, sleeve 66also collapses around conductor 54, sealing this potential point offluid entry as well. Slot 64 in ring electrode 18 is filled with medicaladhesive 70, to complete the assembly. In order to improve themechanical interconnection of the components of the lead, the Tefzel®plastic insulation of the multiconductor coil 34 and Teflon® plastictubing 62 are treated with Chemgrip or by glow discharge (plasma) toactivate their surfaces to enhance adhesion to the sleeve 66 and tosilicone medical adhesive 70. A polyurethane glue, comprised ofPellethane® 2363-75D in N,N-dimethyl acetamide, is applied to the sleeve66 and subsequently air dried to enhance adhesion to silicone medicaladhesive. Adhesion promoters, such as Dow Corning® Z-6020 silane (aminoalkyl functional silane), may be applied to metal or plastic componentsprior to the application of medical adhesive to further improve themechanical interconnection of the lead components.

The resulting assembly provides a structure which is tightly sealedagainst fluid entry, and which displays a high tensile strength throughthe area of the ring electrode. This structure also provides a gradualtransition in flexibility from the ring electrode 18 proximally anddistally, through the combination of sleeve 66 and adhesive 68 and 70.In addition, the structure allows for the fabrication of a substantiallysmaller diameter ring electrode than possible using assemblies whichrequire crimping or swaging cores, as disclosed in U.S. Pat. No.4,328,812, issued to Ufford et al, discussed above.

Although the particular embodiment disclosed in this application takesthe form of a cardiac pacing lead, the inventions disclosed herein arebelieved equally applicable to medical electrical leads in general. Inconjunction with the above description,

we claim:
 1. A connector pin assembly, comprising:an elongatedconductive connector pin having a proximal end and a distal end; a firstinsulative sheath coaxially mounted around said connector pin, saidfirst insulative sheath terminating proximal to the distal end of saidconnector pin; first connector ring mounted around said first insulativesheath, said first connector ring having a proximal end a distal end,the distal end of said first connector ring terminating proximal to thedistal end of said connector pin; a first conductive extensionelectrically and mechanically coupled to the distal end of saidconnector ring and extending distally therefrom; a first electricalconductor coupled to the distal end of said connector pin; and a secondconductor electrically and mechanically coupled to the distal end ofsaid extension.
 2. A connector assembly according to claim 1 furthercomprising an outer, insulative sheath extending distally from saidconnector ring, enclosing the distal end of said first connector ring,said first extension and said first and second conductors.
 3. Aconnector assembly according to claim 1 or claim 2 further comprising anadhesive back-filled between and coupled to said connector pin and saidfirst extension.
 4. A connector assembly according to claim 1, furthercomprising a second insulative sleeve mounted to and surrounding thedistal end of said first connector pin and the proximal portion of saidextension;a second connector ring mounted to and surrounding the distalportion of said second insulative sleeve, said second connector ringhaving a proximal end and a distal end; a second conductive extensioncoupled to the distal end of said second connector ring and extendingdistally therefrom; and a third electrical conductor electrically andmechanically coupled to the distal end of said second extension.
 5. Aconnector assembly according to claim 4, further comprising aninsulative sheath enclosing said second extension and said first, secondand third conductors.
 6. An implantable electrical lead,comprising:first and second mutually insulated elongated conductorshaving proximal and distal ends; a first elongated insulative sheathcovering said first and second conductors; and a connector pin assemblymounted to the proximal end of said first and second conductors,comprising:a connector pin having a proximal end and a distal end; asecond insulative sheath mounted around said connector pin, terminatingproximal to the distal end of said connector pin and terminating distalto the proximal end of said connector pin; a connector ring mountedaround said connector pin and said second insulative sheath, saidconnector ring terminating proximal to the distal end of said connectorpin and distal to the proximal end of said first insulative sheath; aconducive extension coupled to said connector ring, extending distallyfrom said connector ring to a point distal to the distal end of saidconnector pin; and a third insulative sheath extending distally fromsaid connector ring and enclosing said conductive extension; and whereinsaid first and second conductors are electrically coupled to the distalend of said connector pin and to said conductive extension,respectively.
 7. An implantable electrical lead according to claim 6wherein said second insulative sheath is provided with at least onesealing ring extneding outwardly from said second insulative sheath,proximal to said connector ring; andwherein said third insulative sheathincludes at least one sealing ring extending outwardly from said thirdinsulative sheath distal to said connector ring.